add zoom option to camera to work around the orthographic camera

src/rendering/twn_draw.c

@@ -413,7 +413,7 @@ void render(void) {
 }
 
 
-void draw_camera(Vec3 position, Vec3 direction, Vec3 up, float fov) {
+void draw_camera(Vec3 position, Vec3 direction, Vec3 up, float fov, float zoom) {
     bool const orthographic = fabsf(0.0f - fov) < 0.00001f;
     if (!orthographic && fov >= M_PIf)
         log_warn("Invalid fov given (%f)", (double)fov);
@@ -423,6 +423,10 @@ void draw_camera(Vec3 position, Vec3 direction, Vec3 up, float fov) {
         .pos = position,
         .target = direction,
         .up = up,
+        .viewbox = {
+            (Vec2){ 1/-zoom, 1/zoom },
+            (Vec2){ 1/zoom, 1/-zoom }
+        },
     };
 
     if (!orthographic)
@@ -439,7 +443,8 @@ DrawCameraFromPrincipalAxesResult draw_camera_from_principal_axes(Vec3 position,
                                                                   float roll,
                                                                   float pitch,
                                                                   float yaw,
-                                                                  float fov)
+                                                                  float fov,
+                                                                  float zoom)
 {
     bool const orthographic = fabsf(0.0f - fov) < 0.00001f;
     if (!orthographic && fov >= M_PIf)
@@ -460,6 +465,10 @@ DrawCameraFromPrincipalAxesResult draw_camera_from_principal_axes(Vec3 position,
             yaws * pitchc,
         })),
         .up = (Vec3){0, 1, 0},
+        .viewbox = {
+            (Vec2){ 1/-zoom, 1/zoom },
+            (Vec2){ 1/zoom, 1/-zoom }
+        },
     };
 
     if (!orthographic)

src/twn_camera.c

@@ -59,15 +59,15 @@ Matrix4 camera_orthographic(const Camera *const camera) {
 
     Matrix4 result = {0};
 
-    const float rl =  1.0f / (float)1;
-    const float tb =  1.0f / (float)1;
+    const float rl =  1.0f / (camera->viewbox[0].y - camera->viewbox[0].x);
+    const float tb =  1.0f / (camera->viewbox[1].x - camera->viewbox[1].y);
     const float fn = -1.0f / (CAMERA_FAR_Z - CAMERA_NEAR_Z);
 
     result.row[0].x =  2.0f * rl;
     result.row[1].y =  2.0f * tb;
     result.row[2].z =  2.0f * fn;
-    result.row[3].x = -(float)1   * rl;
-    result.row[3].y = -(float)1  * tb;
+    result.row[3].x = -(camera->viewbox[0].y + camera->viewbox[0].x)  * rl;
+    result.row[3].y = -(camera->viewbox[1].x + camera->viewbox[1].y)  * tb;
     result.row[3].z =  (CAMERA_FAR_Z + CAMERA_NEAR_Z) * fn;
     result.row[3].w =  1.0f;
 

src/twn_camera_c.h

@@ -13,6 +13,7 @@ typedef struct Camera {
     Vec3 target;     /* normalized target vector */
     Vec3 up;         /* normalized up vector */
     float fov;       /* field of view, in radians */
+    Vec2 viewbox[2]; /* othrographic aabb, ((left, right), (top, bottom)) */
 } Camera;
 
 Matrix4 camera_look_at(const Camera *camera);